Torque limit wrench

ABSTRACT

A torque limit wrench including a wrench head having a lever arm projecting therefrom, such lever arm being pivotally coupled with an operating handle. A latch normally latches the handle against rotation in its operating position. Limit means is connected with the latch and is operative in response to application of a predetermined force to the handle to release the latch to free the handle for rotation to its inoperative position thus preventing an operator from over-tightening a work piece being manipulated by such wrench head.

United States Patent [1 1 Knoll TORQUE LIMIT WRENCH [75] Inventor: William A. Knoll, Santa Ana, Calif.

[73] Assignee: .IO-Line Tools, Inc., Anaheim, Calif.

[22] Filed: Sept. 30, 1974 [211 App]. No: 510,578

4 1 July 8,1975

Primary Examiner-James L. Jones, Jr. Attorney. Agent, or Firm-Fulwider, Patton, Rieber, Lee & Utecht [57] ABSTRACT A torque limit wrench including a wrench head having a lever arm projecting therefrom, such lever arm being pivotally coupled with an operating handle. A latch normally latches the handle against rotation in its operating position. Limit means is connected with the latch and is operative in response to application of a predetermined force to the handle to release the latch to free the handle for rotation to its inoperative position thus preventing an operator from over-tightening a work piece being manipulated by such wrench head.

11 Claims, 5 Drawing Figures TORQUE LIMIT WRENCH BACKGROUND OF THE INVENTION l. Field of the Invention The present invention relates generally to torque wrenches and more particularly to a torque wrench which is rendered inoperative upon application of a predetermined torque.

2. Description of the Prior Art It has been common practice to provide torque limit wrenches which include a clutch arrangement, but such clutches are generally prohibitively expensive to manu facture.

SUMMARY OF THE INVENTION The torque limiting wrench of the present invention includes a handle pivotally coupled to a work piece head and is normally latched in its operative position by means of a latch. A limit device is responsive to a predetermined torque to release the latch and render the handle inoperative for further torque application.

The objects and advantages of the present invention will become apparent from a consideration of the following detailed description when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a broken top view of a torque limit wrench embodying the present invention;

FIG. 2 is a longitudinal sectional view in enlarged scale taken along the line 2-2 of FIG. 1;

FIG. 3 is a longitudinal sectional view taken along the line 3-3 of FIG. 2;

FIG. 4 is a transverse sectional view taken along the line 4-4 of FIG. 2; and

FIG. 5 is a longitudinal sectional view taken along the line 5-5 of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. 1 and 2, the torque limit wrench of the present invention includes, generally. a wrench socket head 11 having a short lever arm 13 projecting therefrom for engagement with a torque limit device 15. An operating handle, generally designated 17, is pivotally connected to the head 11 by means of a pivot joint, generally designated 19, and a pivotal latch, generally designated 21, is provided for controlling pivoting of such handle. Consequently, when a predetermined torque is exceeded. the limit device 15 will release the latch 21 thus freeing the handle 17 for rotation to its inoperative position shown in broken lines in FIG. 5.

Referring to FIGS. 1 and 2, the lever arm 13 is formed integrally with the wrench socket member 11 and has a transverse notch 25 (FIG. 3) formed in the end thereof to confront a complementary notch 27 formed in the end of a latch piston 29, such notches having their sides chamfered to slope outwardly and receiving freely therebetween an elongated cam 31 which is square in cross section (FIG. 3). Telescoped loosely over the free end of the lever arm 13 is one extremity of a tubular barrel 35, such barrel being pivotally connected thereto by means of a connecting pin 36.

The limit device 15 is telescoped into the intermediate portion of such barrel 35 and received medially over the exterior thereof is a collar 37 which is externally threaded and has a micro-adjustment sleeve, generally designated 39, received thereover. The sleeve 39 is formed on its forward end with an inwardly tapered conical nose 41 which closely fits the outer periphery of the barrel 35 and is then formed with an enlarged-indiameter length 43 which is internally threaded for screwing over the collar 37. An index pointer 44 is formed on the exterior of the nose 4] for selective registration of torque level scale 48 disposed axially along the barrel 35. The rear extremity of the sleeve 39 is enlarged-in-diameter to form an annular groove 45 defining a rearwardly facing shoulder 46 and is then again enlarged-in-diameter to form an internally threaded boss, such boss being knurled on its outer periphery to form a finger grasp adjustment ring 47.

Referring to FIGS. 2 and 4, the barrel 35 is formed medially in its diametrically opposite sides with longitudinally extending slots 51 and 53. A ring 55 is received in the annular groove 45 and is formed on its opposite extremities with radially inwardly projecting fingers 57 and 59 which project inwardly through the respective slots 51 and 53 to engage an annular groove 61 formed in the outer periphery of an annular slider 63 received telescopically within the interior of such barrel 35. The slider 63 serves to compress a compression coil spring 67 against the confronting end of the plunger 29 to maintain such plunger urged axially towards the lever arm 13. The interior of the ring 47 is threaded and has a tubular fitting 68 screwed thereinto to sandwich the ring 55 between one end thereof and the shoulder 46 formed by the groove 45.

Referring to FIG. 2, a pusher tube 71 is telescoped through the coil spring 67 and has its forward extremity received in a blind axial bore 72 formed in the rear face of the plunger 29, the remote extremity of such tube being received telescopically in a through bore 74 formed by an annular pivot fitting 75 mounted in the end of the barrel 35, such remote extremity abutting a latch actuating piston 73.

Referring to FIG. 2, the pivot fitting 75 is formed on its free extremity with a clevis defining a pair of ears 81 and 83 which have aligned through bores 85 and 87 formed therein for receipt of the opposite ends of a pivot tube 91. Received between the ears 81 and 83 is a ring or boss 94 forming one extremity of a handle lever arm 95 and defining a through bore 97 which receives the intermediate portion of the pivot tube 91.

Referring to FIG. 5, such ring 94 is formed in its periphery with a latching notch 103 disposed on the extended radius of the pivot tube 91 for receipt of the free end of the latch 21. In order to provide balanced forces to enable the handle 107 to freely release it is desirable to balance the forces required to unlatch such handle with the frictional forces resisting unlatching. In furtherance of this object, for stainless steel construction, where the coefficient of friction is approximately 0. l 3, it can be shown that the notch 103 should have its opposite walls 104 sloped outwardly away from one another at angles of 7V2 to the radius of the pivot tube 91. It can be shown that for any material such slope should be selected as the arc tangent of the coefficient of friction. Carried from the free end of the handle lever 95 is a tubular handle 107, such handle being mounted from the lever arm by means of a pivot pin 109.

As best seen in FIGS. 2 and 3, the latch 21 is received between the inner extremities of the ears 8] and 83 and is carried on one end from the pivot pin 113. The cam 31 is somewhat L-shaped and is formed on its free extremity with a radially inwardly turned dog 11S disposed on the extended radius of the pivot tube 91 and normally received in the notch 103. The opposite sides of the dog 115 slope outwardly at an angle of 7/2 from the radius of the pivot tube 91 to complement the shape of the walls 104 of the notch 103, it being appreciated that such angle results in the rotary forces applied to the handle 107 tending to dislodge such dog from the notch 103. However, with an angle of 7V2", such forces are exactly balanced by the coefficient of friction between the metal dog 115 and the walls 104 of the notch 103 for stainless steel construction, thus leaving the latch 21 exactly balanced for release from such notch with very little releasing force being applied thereto.

The tail of the latch 21 projects beyond the pivot mounting pin 113 opposite the dog 115 to form a cam surface 121 which is spaced slightly below a longitudinal line passing through the center of the pivot mounting pin 113, thus providing an arrangement whereby movement of the piston 73 to the right, as viewed in FIG. 2, tends to rotate the latch 21 (FIG. counterclockwise to its unlatching position. The latch 21 is normally urged into its latching position by means of a torsion spring 125 wrapped about the pivot mounting pin 113.

In operation, when it is desirable to utilize the torque limit wrench of the present invention in tightening a stud or the like, a socket wrench of the desired size is installed on the socket head 11 and the adjustment ring 47 grasped and rotated to draw the adjustment sleeve 39 forwardly or rearwardly along the barrel 35 as dictated by the pitch of the threads on the collar 37. Rotation of such sleeve 39 is continued until the pointer 41 (FIG. 1) is aligned with the desired torque level as indicated on the scale 48. It will be appreciated that rotation of the sleeve 39 to draw it to the left results in drawing the slider ring 55 to the left, thus drawing the annular slider fitting 63 to the left and compressing the compression coil spring 67 against the plunger 29, thereby applying greater forces to the opposite sides of the release cam 31. Obviously, rotation of the sleeve 39 in the opposite direction will serve to decrease the forces on such cam 31 in a like manner. The socket on the head 11 may then be placed over the head of a stud or the like and the workman may then grasp the handle 107 to rotate the limit wrench, thereby rotating the stud.

It will be appreciated that as tightening continues the force applied to the handle 107 by the workman becomes greater, thus resulting in greater torque being applied to the barrel 35 tending to rotate such barrel about the pivot pin 36 relative to the lever arm 13 (FIG. 2), such rotation being resisted by the compressive forces applied to the cam 31 (FIG. 3) by the plunger 29. However, as the selected torque is reached, the force on the handle 107 will become sufficiently great to cause the compression force of the spring 67 to be overcome by the tendency of the barrel 35 to rotate relative to the lever arm 13 and such barrel will rotate to a misaligned position relative to the lever arm 13 as shown in FIG. 3. Such misalignment of the lever arm 13 causes the square cam 31 to rotate slightly to the cocked position shown in FIG. 3, thus shifting the plunger 29 slightly to the right, as for instance 0.080 inches, thereby compressing the coil spring 67 to shift the latch actuating piston 73 (FIG. 5) to the right and rotating the latch 21 slightly counterclockwise to lift the dog out of the notch 103 thereby releasing the handle 107 for rotation thereof about the pivot pin 91. Consequently, the workman is physiologically prevented from applying additional torque to the stud, thus positively preventing over-tightening of such stud and possible breaking thereof. When the handle 107 is rotated back to its operative position (as shown in FIG. 1) the dog 115 (FIG. 5) will snap back into the notch. thus enabling the latch actuating piston 73 to shift back to the right thereby resulting in the barrel 35 again assuming its aligned position with respect to the lever arm 13 as shown in solid lines in FIG. 3.

It will be appreciated that the limit wrench of the present invention can be utilized to tighten either right or left hand threads and that release of the latch 21 will be symmetrical as a result of the symmetrical arrangement of the notch 103 and dog 115 for release of such dog in either rotational direction from such notch.

From the foregoing, it will be appreciated that the limit wrench of the present invention is relatively economical to manufacture and will provide for foolproof operation to positively prevent over-tightening of the work piece.

Obviously, many modifications and variations of the present invention may be made with regard to the foregoing detailed description without departing from the spirit of the invention.

1 claim:

1. A torque limit wrench for applying a predetermined torque to a work piece and comprising:

work-receiving head means;

handle means;

pivot means coupling said handle to said head;

a latch for latching said pivot means against pivoting;

and

limit means connected with said latch and operative in response to application of a sufficient force to said handle to apply said predetermined torque to said head to release said latch to free said handle for pivoting to render said handle inoperative for applying torque higher than said predetermined torque to said head whereby said head may be received over a work piece, a rotary force applied to said handle to apply said predetermined torque to said work piece and upon application of a rotary force sufficient to apply said predetermined torque to said work piece said limit means will release said latch to render said handle inoperative to thereby positively prevent application of a torque higher than said predetermined force to said work piece.

2. A torque limit wrench as set forth in claim 1 that includes:

torque adjustment means for adjusting said limit means to different selected torque levels; and indicator means on said head for indicating said selected torque level.

3. A torque limit wrench as set forth in claim 1 wherein:

said head means includes a lever arm projecting therefrom and formed on its extremity with a first notch having a substantially flat bottom wall and a barrel having one extremity received telescopically over the free end of said lever arm and pivotally connected therewith; and

said limit means is received in said barrel and includes a plunger formed with a second notch confronting said first notch, a square-in-cross section cam sandwiched between said lever arm and plunger and having its opposite sides received in said notches, said limit means further including bias means urging said plunger towards said lever arm. 4. A torque limit wrench as set forth in claim 1 wherein:

said head means includes lever arm means projecting therefrom and formed on its free extremity with a clevis defining spaced apart ears, said ears being formed with aligned through bores; said handle means includes a boss received in said clevis and formed with a through bore; said pivot means projects through said bores in said clevis and boss; and said latch is mounted in said lever arm for engagement with said clevis. 5. A torque limit wrench as set forth in claim 1 wherein:

said head means includes a lever arm projecting radially of the direction of said predetermined torque; and said handle means is in the form of a hand grasp element for grasping by a workman to manually rotate said work piece. 6. A torque limit wrench as set forth in claim 1 wherein:

said limit means includes an abutment surface on said handle projecting at a predetermined angle to the radius of said pivot means and a latch mounted pivotally on one extremity from said head means and formed on its free extremity with a dog projecting tangentially to said radius and including a latch surface normally engaging said abutment surface, said predetermined angle being equal to the arc tangent of the coefficient of friction between said abutment and latch surfaces. 7. A torque limit wrench as set forth in claim 1 wherein:

said handle means is formed with a latch notch defining opposed abutment surfaces projecting radially of said pivot means; and said latch is pivotaily mounted on one end from said head and is formed on its free extremity with a dog normally received in said latch notch and having its opposite sides defining abutment surfaces for normally engaging said notch abutment surfaces for limiting rotation of said handle in opposite directions about said pivot means. 8. A torque limit wrench as set forth in claim I wherein:

said handle means includes latch notch means; and said latch includes pivotal mount means mounting one extremity of said latch from said head means and is formed on its free extremity with a dog for normally engaging said notch to limit rotation of said head, said latch being further formed on said one extremity with a cam surface offset from the diameter of said mount means and said limit means includes plunger means engaged with said cam surface and operative in response to application of said predetermined torque to rotate said latch about said pivotal mounting means to disengage said dog from said notch to free said handle for rotation about said pivot means. 9. A torque limit wrench as set forth in claim 6 wherein:

said abutment surface projects at an angle of substantially 7%" to the radius of said pivot means. 10. A torque limit wrench as set forth in claim 6 wherein:

said latch surface normally projects coextensive with said abutment surface to engage flush therewith. 11. A torque limit wrench as set forth in claim 2 wherein:

said notch projects radially of said pivot means and is formed with opposed abutment surfaces; and said dog is formed to project tangentially of said mount means and is formed with abutment surfaces projecting parallel with said respective notch abutment surfaces when engaged therewith. 

1. A torque limit wrench for applying a predetermined torque to a work piece and comprising: work-receiving head means; handle means; pivot means coupling said handle to said head; a latch for latching said pivot means against pivoting; and limit means connected with said latch and operative in response to application of a sufficient force to said handle to apply said predetermined torque to said head to release said latch to free said handle for pivoting to render said handle inoperative for applying torque higher than said predetermined torque to said head whereby said head may be received over a work piece, a rotary force applied to said handle to apply said predetermined torque to said work piece and upon application of a rotary force sufficient to apply said predetermined torque to said work piece said limit means will release said latch to render said handle inoperative to thereby positively prevent application of a torque higher than said predetermined force to said work piece.
 2. A torque limit wrench as set forth in claim 1 that includes: torque adjustment means for adjusting said limit means to different selected torque levels; and indicator means on said head for indicating said selected torque level.
 3. A torque limit wrench as set forth in claim 1 wherein: said head means includes a lever arm projecting therefrom and formed on its extremity with a first notch having a substantially flat bottom wall and a barrel having one extremity received telescopically over the free end of said lever arm and pivotally connected therewith; and said limit means is received in said barrel and includes a plunger formed with a second notch confronting said first notch, a square-in-cross section cam sandwiched between said lever arm and plunger and having its opposite sides received in said notches, said limit means further including bias means urging said plunger towards said lever arm.
 4. A torque limit wrench as set forth in claim 1 wherein: said head means includes lever arm means projecting therefrom and formed on its free extremity with a clevis defining spaced apart ears, said ears being formed with aligned through bores; said handle means includes a boss received in said clevis and formed with a through bore; said pivot means projects through said bores in said clevis and boss; and said latch is mounted in said lever arm for engagement with said clevis.
 5. A torque limit wrench as set forth in claim 1 wherein: said head means includes a lever arm projecting radially of the direction of said predetermined torque; and said handle means is in the form of a hand grasp element for grasping by a workman to manually rotate said work piece.
 6. A torque limit wrench as set forth in claim 1 wherein: said limit means includes an abutment surface on said handle projecting at a predetermined angle to the radius of said pivot means and a latch mounted pivotally on one extremity from said head means and formed on its free extremity with a dog projecting tangentially to said radius and including a latch surface normally engaging said abutment surface, said predetermined angle being equal to the arc tangent of the coefficient of friction between said abutment and latch surfaces.
 7. A torque limit wrench as set forth in claim 1 wherein: said handle means is Formed with a latch notch defining opposed abutment surfaces projecting radially of said pivot means; and said latch is pivotally mounted on one end from said head and is formed on its free extremity with a dog normally received in said latch notch and having its opposite sides defining abutment surfaces for normally engaging said notch abutment surfaces for limiting rotation of said handle in opposite directions about said pivot means.
 8. A torque limit wrench as set forth in claim 1 wherein: said handle means includes latch notch means; and said latch includes pivotal mount means mounting one extremity of said latch from said head means and is formed on its free extremity with a dog for normally engaging said notch to limit rotation of said head, said latch being further formed on said one extremity with a cam surface offset from the diameter of said mount means and said limit means includes plunger means engaged with said cam surface and operative in response to application of said predetermined torque to rotate said latch about said pivotal mounting means to disengage said dog from said notch to free said handle for rotation about said pivot means.
 9. A torque limit wrench as set forth in claim 6 wherein: said abutment surface projects at an angle of substantially 7 1/2 * to the radius of said pivot means.
 10. A torque limit wrench as set forth in claim 6 wherein: said latch surface normally projects coextensive with said abutment surface to engage flush therewith.
 11. A torque limit wrench as set forth in claim 2 wherein: said notch projects radially of said pivot means and is formed with opposed abutment surfaces; and said dog is formed to project tangentially of said mount means and is formed with abutment surfaces projecting parallel with said respective notch abutment surfaces when engaged therewith. 